The present invention relates generally to an inertial impaction air sampling device which is small-sized for portability and self-contained allowing for remote or personal sampling, and more particularly, to a portable, personal air sampling device capable of collecting respirable organometallic particulates in room environment air and direct analysis for providing immediate results.
The collection and analysis of elemental containing particulates, especially organometallic particulates in the presence of additional organic sample components, in ambient air is becoming increasingly important as maximum permissable exposure to toxic agents decreases. Accordingly, the relationship between the sampling method and the analytical method is becoming increasingly important. The particular analyte to be determined, as well as the particular sampling method chosen, will generally dictate the analytical procedure that can be used, and conventional sampling devices have not always proved satisfactory for providing the information desired.
Several air sampling devices are commonly known for collecting particulates in room air. Bulk or wipe samples do not yield useful information about airborne concentrations of contaminants. Filter sampling is not always reliable since filter loading can occur rapidly with membrane filters, and contaminants or oversized particles can be collected that would suggest higher than actual exposure. Also, no particle size distribution is obtainable without further analysis by electron microscopy or some other analytical technique. Further, filter samples generally require extensive treatment prior to the analysis, a process that is time consuming, expensive, and subjects the entire procedure to increased probability of errors.
Atomic absorption spectrometry offers advantages in the analysis of elemental containing particulates because it can provide low detection limits (more sensitive detection) and precise determinations for a wide variety of elements, and is thus very popular for non-real-time determinations. However, real time sampling would be optimum and would eliminate the potential problems associated with sample collection methods, sample transport, and sample preparation, and real time sampling has heretofore not been possible with atomic absorption spectrometry. Real time sampling would require, first, that an atomic absorption spectrometer be present in the vicinity of the sample being collected and, second, that multiple instruments be available should several sites be needed to be sampled simultaneously. This is neither economical or practical where the determination of occupational exposure must be made from a breathing zone sample, the "breathing zone" being commonly known as the space within one foot of the mouth and nose of the worker in an occupational environment.
Also, traditional atomic absorption methods utilize the sample in the form of a solution. Airborne particulates, however collected, must be subjected to a dissolution procedure, usually requiring acid digestion and a dilution process. These processes cause undesirable sample losses as do the pretreatment processes for filter sampling.
Additionally, specific methods for sampling and analysis using atomic absorption spectrophotometry have suffered from various specific disadvantages. Impinger samplers used with UV/VIS Absorption Spectrophotometry have been plagued with matrix interferences which preclude sensitive and precise detection of various organometallic elements, for instance hexaphenyl dilead in the presence of styrene. Filter collection methods used with Flame Atomic Absorption have been shown to have excessive loss of the sample. Because of the additional losses in the sample preparation for analysis, the overall efficiency of this method is less than 25% with poor precision.
The most precise and sensitive analytical method for sampling and detecting organometallic constituents in ambient air is inertial impaction sampling, a method which collects the sample in such a way that it can be deposited directly into the analytical measurement system, e.g. the spectrometer sample cell, combined with Graphite Furnace Atomic Absorption (GFAA) analysis. Compared with flame atomic absorption, this method of analysis offers low detection units, electrothermal atomization, more absorption, more sensitive detection--results using this method are approximately three orders of magnitude better than detection using flame atomic absorption--and the elimination of all sample pretreatment steps. However, in the past, inertial impaction has been limited to quantitative rather than qualitative analysis. Also, when inertial impaction samplers have been combined with graphite furnace impaction substrates, the furnace itself has been permanently mounted in the electrothermal atomization atomic absorption spectrometer, and a tapered collection device was inserted into the furnace for analysis. While this method is useful in the development of an area monitoring system for a workplace environment, it is not useful in the case of the determination of occupational exposure where samples must be collected in the breathing zone of the worker. Nevertheless, inertial impaction has been shown to be extremely efficient in the collection of respirable size particles (1-20 .mu.m aerodynamic diameter), with entry losses in the range of 8-16% for particles from 1-7 .mu.m aerodynamic diameter, and inertial impaction sampling plus GFAA analysis has proved to be the best sampling and analysis method for the determination of airborne organometallic particulates.
There is an existing need for a reliable and economical air sampling device to be used for both quantitative and qualitative analysis of materials in the environment.
Also, there is an existing need for an inertial impaction device designed as a personal breathing zone sampler, capable of size selective sampling of respirable size particles in the ambient environment (1-20 microns in diameter), low detection limits, and rapid, direct analysis without the need for extended sample preparation procedures.
There is a further need for a personal breathing zone sampler that is portable and attachable to an individual in the workplace, and that operates at a flow rate which closely approximates the rate of human respiration (2.0 L/min.).
There is still a further need for a personal breathing zone sampler device using a graphite furnace as the impaction substrate.